“I think it’s actually the first example of using bad breath as a defense, although I’m sure that everybody has had a personal encounter of something similar,” says Ian Baldwin of the Max Planck Institute for Chemical Ecology in Jena, Germany.

As a plant defense, nicotine works by poisoning a variety of creatures. But the plump, striped tobacco hornworm caterpillar (Manduca sexta) can repurpose the poison to generate “toxic halitosis,” Baldwin says.

When a hornworm feeds on a wild tobacco plant, a touch of the plant’s nicotine is diverted into the insect equivalent of a bloodstream. Baldwin and his colleagues identified a gene that is involved in diverting 0.65 percent of ingested nicotine to create smoker’s breath strong

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